EPA Expresses Concern Regarding Potential Development of 2,4-D-Resistant Weeds

I am not surprised that the U.S. Environmental Protection Agency (EPA) went ahead and registered Enlist Duo™, Dow Agrosciences’ pesticide cocktail made for spraying on corn and soybean crops genetically engineered (GE) to be tolerant of it.

Disappointed, yes. Surprised? No.

Now, it’s only a matter of time before American farmers will have an even bigger superweed problem than they already have, the current problem in large part the result of previous registration by EPA of glyphosate, the active ingredient in Roundup®, for use on the millions and millions of acres of farms where GE corn, GE soybeans and other GE crops are grown in the United States.

Even the EPA shares my concern.

As it states in its Response to Public Comments Received Regarding New Uses of Enlist DuoTM on corn and soybean:

“The Agency agrees that the registration of Enlist Duo™ for use on Enlist seed presents the potential for growers to over-rely on a single product that contains two herbicidal active ingredients. If it happens, the over-dependence can increase the selection pressure on weeds and lead to resistance.”

EPA goes on to state that “because herbicide use on herbicide-resistant crops presents this increased risk…of the likelihood of the development of resistant weeds and their associated impacts…the Agency is addressing resistance potential in this registration in an unprecedented manner.”

At one point that unprecedented manner included a requirement listed on Enlist Duo™ labels to “scout fields before and after herbicide application, which is consistent with integrated pest management (IPM) and is essential to early identification of lack of herbicide efficacy that could be an early sign of weed resistance. The critical importance of scouting is widely recognized by research and extension specialists in pest control and should be practiced when using Enlist Duo™ or other pesticides.”

However, although the “Agency firmly believes that it is a good best management practice to scout…[it] also recognizes that on-field weed resistance is best managed by the grower who understands his or her specific situation. Therefore, the requirement [emphasis added] to scout fields 7-21 days after application will not be imposed, but the labels will contain recommendations [emphasis added] for field scouting.”

In the end, the “terms of registration for Enlist Duo™ place the responsibility on the registrant [Dow Agrosciences] for reducing the potential for resistance or to significantly delay the onset of resistance.”  The “Agency is requiring that [Dow Agrosciences] have an Herbicide Resistance Management (HRM) Plan in place…[and] is also requiring the registrant to develop education and training programs that will provide growers with the best available information on herbicide resistance management…. The HRM Plan…will involve [Dow Agrosciences] working with growers to help identify early signs of weed resistance and to resolve the problem before it spreads. The HRM Plan also requires education and reporting to the Agency.”

Will putting the onus on the registrant for managing this critical issue do the trick?

History suggests not.

EPA also put the onus for managing the critical issue of keeping GE StarLink™ corn and the potential human allergen it produced out of the human food supply on the registrant of that product. That registrant’s management plan failed in a matter of months when that GE corn showed up in the human food chain in the United States. Not only that, but the wayward StarLink™ corn was detected in human food on grocery shelves only through the efforts of an NGO, not the efforts of the “responsible” registrant. StarLink™ corn remained detectable in US corn crops, at levels of concern to the US Centers for Disease Control and Prevention, for at least another seven years after EPA revoked its registration.

EPA has imposed a 6-year limit on registration of Enlist Duo™, partly to allow it to reassess the “superweed” issue. But, based on both history and biology, the increased selection pressure imposed by using Enlist Duo™ will most certainly result in significantly more 2,4-D-resistant weeds–and more glyphosate-resistant weeds than are already out there as well–and US farmers are bound to have an even bigger superweed problem by the EPA’s 2020 registration deadline.

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One Response to EPA Expresses Concern Regarding Potential Development of 2,4-D-Resistant Weeds

  1. Pingback: Exposure of Mammals, Birds, Reptiles and Land-Phase Amphibians to Dow Agrosciences’ Pesticide Cocktail? | Biotech Salon

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